IF i was taking a punt, I'd take a stab at us going for a top quality young left back as Baines understudy/eventual replacement.
City are signing Mendy, the rs brought in Robertson, Arsenal signed Kolasanic, Chelsea are already set at that position as are Spurs, so only United who maybe do need one. Think we may be sitting tight see who they all go for and then go for one ourselves.
Koeman has bought from Celtic before in both Wanyama, VVD and Forster to good effect (or if not bought them all at least worked well with all 3), Tierney is highly touted and unlikely to be available till after they play their CL qualifier - IF all the other teams have brought in a young left back already, then it will pretty much give us a free run at him - as no one below us would be able to compete for him.
Least thats my hope.